Electricity and Heat Production: This is the largest single source of global greenhouse gas emissions due to the burning of coal, natural gas, and oil for electricity and heat. The emissions are primarily carbon dioxide, with smaller amounts of methane and nitrous oxide.

Transportation: The transport sector, including cars, trucks, ships, trains, and planes, is a major emitter of CO2, particularly from the combustion of petroleum-based products like gasoline and diesel. There are also emissions of methane and nitrous oxide from internal combustion engines and the production and distribution of fuels.

Residential and Commercial Buildings: Emissions from this sector arise from on-site energy use for heating, cooling, lighting, and operating appliances. In many parts of the world, these emissions come from the combustion of fossil fuels, either directly in buildings or indirectly through the use of electricity.

Manufacturing and Construction: Industries such as steel, cement, chemical, and others emit a significant amount of CO2 through the chemical processes involved in production. For example, cement production releases CO2 when limestone (calcium carbonate) is converted to lime (calcium oxide).

Fugitive Emissions: These are emissions that escape into the atmosphere during the extraction, processing, and delivery of fossil fuels. Methane leakage from oil and natural gas systems is a significant contributor.

Agriculture: Agricultural activities contribute to emissions in several ways, including enteric fermentation in ruminants, which produces methane; manure management, which can release methane and nitrous oxide; rice paddies, which are significant methane sources; and the use of synthetic fertilizers, which emit nitrous oxide.

Land Use and Forestry: Deforestation, land clearing for agriculture, and degradation of soils contribute to emissions. Conversely, this sector also has the potential to act as a carbon sink through reforestation, improved land management, and conservation.

Landfills: Decomposing organic waste in landfills produces methane. The waste sector's contribution to global greenhouse gas emissions is significant, particularly in countries where waste management practices are less developed.

Wastewater Treatment and Disposal: This can also produce methane and nitrous oxide emissions, depending on the treatment technology used.

Chemical Production: The production of chemicals like ammonia and the use of refrigerants can release various greenhouse gases, including fluorinated gases, which have a high global warming potential.

Mineral Production: The mineral extraction and production process, particularly for metals, can result in significant CO2 emissions.

Oil and Gas Production: Methane is a primary concern here, as it can be released during drilling, extraction, and transportation of these fuels.

Coal Mining: Coal mining releases methane that is trapped within coal seams.

Energy Intensity: The energy intensity of any industry or sector, which is the amount of energy consumed per unit of output, can affect its emissions profile.

Technological Development: The adoption of new technologies and practices can significantly influence the emissions of any sector, often leading to reductions.